Most all cathode ray tubes (CRTs), such as those used in television sets, computer monitors and the like emit electromagnetic radiation. The measured intensity of the electromagnetic radiation is directly proportional to the proximity of the measurement to the CRT. In other words, the closer a person is to the CRT, the more intense the electromagnetic radiation becomes. Unfortunately, electromagnetic radiation is suspected of being a health hazard. Exposure to electromagnetic radiation has been implicated as being the cause, or partial cause, of several types of cancer and neurological disorders. Similarly, over exposure to electromagnetic radiation is suspected to increase birth defects and increase the chances for a miscarriage.
Another harmful effect, also associated with CRTs, is caused by the optical brightness of the image being produced by the CRT. This danger affects the eyes of the viewer and is also proportional to the distance between the viewer and the CRT. As a result, the brightness of the image is more intense the closer to the CRT a person stands. Watching an over bright CRT at a location too close to the CRT can cause physical damage to the eye that permanently effects a person's vision.
With the growing popularity of television, personal computers, video games and the like, people are spending more and more time sitting and standing in front of CRTs. As a result, people are experiencing larger doses of electromagnetic radiation. The problem is even more prevalent with young children. Young children tend to watch more television and play more computer video games than typical demographic groups. Additionally, children typically do not recognize the dangers presented by video monitors and tend to stand or sit directly in front of the video monitor when watching television or playing a game. As a result, there exists a need for a device that will prevent a child or another person from overexposing themselves to the electromagnetic radiation and other harmful effects of a CRT.
In the prior art there are many devices that are either activated or deactivated by the close proximity of a person to that device. Such devices are commonly used to automatically open and close doors or to turn on and off lights. Similarly, such devices exist in the field of security, such as motion detectors for activating alarms. Most proximity detectors detect the presence of a person either by sensing a physical characteristic, such as the thermal heat or vibrations produced by the person, or by measuring a disruption in a transmitted signal. Examples of the latter include ultrasonic detectors, photodetectors, and Hall effect detectors that measure changes in a projected electromagnetic field. Specific examples of proximity detectors, used in the prior art to turn on and off equipment, include U.S. Pat. No. 5,047,752 to Schorn, entitled SAFETY SYSTEM FOR A MACHINE TOOL. In the Schorn patent a machine tool of any given design is equipped with an array of ultrasonic transmitters and receivers, which act as proximity sensors. If a person wanders too close to the machine tool while it is running, the person's presence is detected and the machine tool is automatically disabled. The Schorn patent also includes a range adjuster for adjusting the effective range of the ultrasonic transmitters and a timing circuit to delay the deactivation of the machine tool for a predetermined period of time.
Although the prior art record shows various devices that are automatically activated or deactivated by the proximity of a person, such prior art devices are not readily adaptable for use with a video monitor in a domestic environment. Video monitors in the home, (i.e. television sets and computer monitors) are typically positioned in areas of a home experience traffic. As a result, if a simple on/off proximity circuit were coupled to the video monitor, it would constantly be turned on and off. This is highly disruptive to any person watching the video monitor. Furthermore, the constant cycling on and off of the monitor can cause damage. Even prior art proximity systems that have time delays are not well suited for application with a video monitor in a domestic setting. In the environment of a person's home, it is very common for a person to pause in one area to talk to another person or to do any other every day activity. As such, a video monitor with a simple time delay would also constantly cycle on and off, again disrupting the person watching the monitor and causing harm to the monitor itself.
It is therefore and objective of the present invention to provide a proximity controlled safety device for a video monitor that prevents a person from overexposure to electromagnetic radiation and optical brightness yet is not harmful to the video monitor and is not disruptive in a domestic environment.
It is another object of the present invention to provide such a proximity controlled safety device that can be retroactively added to most any existing video monitor or can be integrally formed as part of any new video monitor.